The present invention relates generally to the construction of a lens barrel for use in a camera, and more particularly to the arrangement of cylinder elements which form the structure of such a lens barrel.
The structure of a camera lens barrel typically includes a plurality of cylinder elements which are arranged in overlapping relation to each other. The innermost cylinder of this arrangement supports a lens to perform a photographic function. The various cylinders of the arrangement are mechanically interconnected so that when the outermost cylinder element is manually moved or adjusted, the innermost cylinder element will also be moved in response to the movement of the outermost cylinder element. If, as a result of any external forces applied to the arrangement, any of the cylinder elements should become distorted, frictional forces between the various cylinder elements will increase, thus preventing the smooth movement of the various cylinder elements.
In order to prevent such distortion, conventional lens barrels use metallic cylinder elements which have built up or enlarged radial wall thicknesses. This, however, tends to increase the weight of the lens barrel.
The foregoing disadvantage can be eliminated by either decreasing the wall thickness of the metallic cylinder elements, or by forming the cylinder elements out of a material which has a lower specific gravity than the typical metallic materials used.
Decreasing the wall thickness of the cylinder elements is generally unsatisfactory since this tends to increase the chances of deforming the cylinder elements even when a small external force is applied. Therefore, even though the weight of the lens barrel will be decreased by decreasing the wall thickness of the cylinder elements, the principal objective of preventing the cylinder elements from becoming deformed is not achieved.
Using cylinder elements made of materials having a lower specific gravity than metal will also tend to decrease the weight of the lens barrel. However, materials such as plastic are generally one third to one fifth the strength of the typical metallic materials and such plastic cylinder elements tend to be deformed more easily than metallic cylinder elements when external forces are applied to the arrangement of cylinders.
Cylinder elements which are made of plastic material therefore must have wall thicknesses which are significantly larger than the wall thicknesses of cylinder elements made out of metal in order for such elements to be equal in strength to the metallic cylinder elements. An increase in the wall thicknesses of the various cylinder elements causes the outer diameter of the lens barrel to be significantly enlarged, which is also an undesirable feature in lens barrels.
It is accordingly, a principal object of the present invention to provide an improved arrangement of cylinder elements for a lens barrel which generally overcomes the disadvantages of the prior art.
It is a more specific object of the present invention to provide an arrangement of cylinder elements which can produce a light weight lens barrel.
A further object of the present invention is to provide such an arrangement of cylinder elements for use in a lens barrel which can be made of metallic material having thin walls without increasing its susceptibility to deformation upon the application of external forces.
It is still a further object of the present invention to permit the use of cylinder elements made out of plastic material without increasing the overall size of the lens barrel while maintaining desired strength for the various cylinder elements.
Other objects, features and advantages of the invention will be apparent from the description of the invention in connection with the accompanying drawings, which will be described more fully hereinafter.